U.S. patent application number 16/301708 was filed with the patent office on 2019-10-17 for contact lens and method for manufacturing the same.
This patent application is currently assigned to HOYA CORPORATION. The applicant listed for this patent is HOYA CORPORATION. Invention is credited to Takaharu NAKAJIMA, Yohei SAWADA, Naoki TSUJI.
Application Number | 20190317337 16/301708 |
Document ID | / |
Family ID | 60783461 |
Filed Date | 2019-10-17 |
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United States Patent
Application |
20190317337 |
Kind Code |
A1 |
SAWADA; Yohei ; et
al. |
October 17, 2019 |
CONTACT LENS AND METHOD FOR MANUFACTURING THE SAME
Abstract
There is provided a contact lens having a convex front surface
and a concave rear surface, the front surface being divided into an
optical portion, an edge joining the front and rear surfaces, a
first smoothing portion arranged on an outer periphery of the
optical portion, a peripheral portion arranged on an outer
periphery of the first smoothing portion, and a second smoothing
portion connecting the peripheral portion and the edge, the front
surface having mirror image symmetry with respect to a vertical
meridian as a boundary extending from an upper end of the lens to a
lower end of the lens passing through a midpoint of the lens, and
having mirror image symmetry also with respect to the horizontal
meridian perpendicular to the vertical meridian at the lens
midpoint, the peripheral portion being arranged to include the
horizontal meridian, and configured of: a first peripheral portion
arranged to include the horizontal meridian and having a shape so
as to maximize a thickness of the contact lens on the horizontal
meridian, a second peripheral portion arranged to include the
vertical meridian and having a shape so as to minimize the
thickness of the contact lens on the vertical meridian, a first
peripheral auxiliary portion which is a portion adjacent to the
first peripheral portion, having a surface shape so as to keep the
thickness of the contact lens constant; and an inclined portion
which is a portion connecting the first peripheral auxiliary
portion and the second peripheral portion to form a continuous
surface, and having a surface shape that changes the thickness of
the contact lens.
Inventors: |
SAWADA; Yohei; (Tokyo,
JP) ; NAKAJIMA; Takaharu; (Tokyo, JP) ; TSUJI;
Naoki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HOYA CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
HOYA CORPORATION
Tokyo
JP
|
Family ID: |
60783461 |
Appl. No.: |
16/301708 |
Filed: |
November 25, 2016 |
PCT Filed: |
November 25, 2016 |
PCT NO: |
PCT/JP2016/084987 |
371 Date: |
November 14, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02C 7/044 20130101;
G02C 7/04 20130101; G02C 7/041 20130101; G02C 7/048 20130101 |
International
Class: |
G02C 7/04 20060101
G02C007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 2016 |
JP |
2016-121418 |
Claims
1. A contact lens having a convex front surface and a concave rear
surface, the front surface being divided into an optical portion,
an edge joining the front and rear surfaces, a first smoothing
portion arranged on an outer periphery of the optical portion, a
peripheral portion arranged on an outer periphery of the first
smoothing portion, and a second smoothing portion connecting the
peripheral portion and the edge, the front surface having mirror
image symmetry with respect to a vertical meridian as a boundary
extending from an upper end of the lens to a lower end of the lens
passing through a midpoint of the lens, and having mirror image
symmetry also with respect to the horizontal meridian perpendicular
to the vertical meridian at the lens midpoint, the peripheral
portion being arranged to include the horizontal meridian, and
configured of: a first peripheral portion arranged to include the
horizontal meridian and having a shape so as to maximize a
thickness of the contact lens on the horizontal meridian, a second
peripheral portion arranged to include the vertical meridian and
having a shape so as to minimize the thickness of the contact lens
on the vertical meridian, a first peripheral auxiliary portion
which is a portion adjacent to the first peripheral portion, having
a surface shape so as to keep the thickness of the contact lens
constant; and an inclined portion which is a portion connecting the
first peripheral auxiliary portion and the second peripheral
portion to form a continuous surface, and having a surface shape
that changes the thickness of the contact lens.
2. The contact lens according to claim 1, wherein a radial width of
the peripheral portion is constant.
3. The contact lens according to claim 1, wherein a surface area
ratio of the peripheral portion to the front surface is 1:99 to
10:90.
4. The contact lens according to claim 1, wherein a thickness in
the first peripheral portion when viewed in a radial direction is
constant.
5. The contact lens according to claim 1, wherein a thickness in
the first peripheral portion viewed in a circumferential direction
is decreased when rotating from the horizontal meridian to the
vertical meridian.
6. The contact lens according to claim 1, wherein a thickness in
the second peripheral portion viewed in a radial direction is
constant.
7. The contact lens according to claim 6, wherein a radial width of
the first peripheral auxiliary portion is decreased when rotating
from the horizontal meridian to the vertical meridian, a radial
width of the second peripheral portion is increased from the
horizontal meridian to the vertical meridian, and a boundary
between the inclined portion and the second peripheral portion is
parallel to the horizontal meridian.
8. The contact lens according to claim 1, wherein the optical
portion is formed by a toroidal surface having an astigmatism
correcting function.
9. The contact lens according to claim 1, wherein in the optical
portion, regions of different powers are arranged in an elliptical
shape, including a distance vision portion for a distance vision
arranged at a center of the optical portion, and a first
intermediate portion arranged on an outer periphery of the distance
vision portion and having a power distribution continuously
increasing from the power of the distance vision portion, and a
near vision portion for a near vision arranged on the outer
periphery of the first intermediate portion.
10. The contact lens according to claim 1, wherein in the optical
portion, regions of different powers are arranged in an elliptical
shape, including the near vision portion arranged at a center of
the optical portion, a second intermediate portion arranged on an
outer periphery of the near vision portion and having a power
distribution continuously decreasing from the power of the near
vision portion, and a distance vision portion arranged on an outer
periphery of the second intermediate portion.
11. The contact lens according to claim 1, wherein a material of
the contact lens is a hydrogel or a silicone hydrogel.
12. The contact lens according to claim 1, wherein a center
thickness in the optical portion is in a range of 0.05 to 0.20
mm.
13. The contact lens according to claim 1, wherein within a
predetermined rotation angle range of the rotation from the
horizontal meridian to the vertical meridian in the peripheral
portion, the first peripheral auxiliary portion is arranged on one
side of an inner peripheral side or an outer peripheral side, and
the inclined portion is arranged on the other side of the inner
peripheral side or the outer peripheral side, so that the both are
made to coexist.
14. The contact lens according to claim 13, wherein the first
peripheral auxiliary portion is arranged on the inner peripheral
side and the inclined portion is arranged on the outer peripheral
side so that the both are made to coexist.
15. The contact lens according to claim 1, wherein a shape of the
peripheral portion is made to be elliptical and annular having a
long axis in the horizontal direction.
16. A method for manufacturing a contact lens using a cast mold
manufacturing method, the contact lens having a convex front
surface and a concave rear surface, the front surface being divided
into an optical portion, an edge joining the front and rear
surfaces, a first smoothing portion arranged on an outer periphery
of the optical portion, a peripheral portion arranged on an outer
periphery of the first smoothing portion, and a second smoothing
portion connecting the peripheral portion and the edge, the front
surface having mirror image symmetry with respect to a vertical
meridian as a boundary extending from an upper end of the lens to a
lower end of the lens passing through a midpoint of the lens, and
having mirror image symmetry also with respect to the horizontal
meridian perpendicular to the vertical meridian at the lens
midpoint, the peripheral portion being arranged to include the
horizontal meridian, and configured of: a first peripheral portion
arranged to include the horizontal meridian and having a shape so
as to maximize a thickness of the contact lens on the horizontal
meridian, a second peripheral portion arranged to include the
vertical meridian and having a shape so as to minimize the
thickness of the contact lens on the vertical meridian, a first
peripheral auxiliary portion which is a portion adjacent to the
first peripheral portion, having a surface shape so as to keep the
thickness of the contact lens constant; and an inclined portion
which is a portion connecting the first peripheral auxiliary
portion and the second peripheral portion to form a continuous
surface, and having a surface shape that changes the thickness of
the contact lens.
Description
TECHNICAL FIELD
[0001] The present invention relates to a contact lens, and in
particular, to a contact lens having a double slab off as an axis
stabilizing mechanism for increasing a horizontal thickness as
compared to a vertical thickness of a contact lens, and a method
for manufacturing the same.
DESCRIPTION OF RELATED ART
[0002] Contact lenses are widely used for correcting visual
impairment, for example. The visual impairment includes, for
example, myopia, hyperopia, astigmatism and presbyopia. Myopia or
hyperopia is a state in which parallel light beams are focused in
front of or behind a retina in a state of not exerting an
adjustment power, and one of correction methods for myopia and
hyperopia is a contact lens (also called a myopic/hyperopic lens).
Astigmatism is a state in which light emitted from one point of an
outside world does not converge to one point in an eye due to a
fact that a cornea or a crystalline lens shape is not a perfect
spherical surface (for example, a refractive index in a vertical
direction differs from a refractive index in a horizontal
direction), and one method of correcting astigmatism is a toric
contact lens (also called astigmatism lens). Presbyopia
(farsightedness) is a state in which power to adjust the focus of
the eye from a distant object to a nearby object is reduced by age,
and one of the correction methods for presbyopia is a multifocal
contact lens (also called a bifocal lens).
[0003] In the toric contact lens, an optical portion is formed by a
toroidal surface for correcting astigmatism, and therefore it is
necessary to stabilize a posture of the lens. Therefore, an axis
stabilizing mechanism is provided around the optical portion. The
axis stabilizing mechanism can be divided into Truncation (Patent
Documents 1 and 2), Ridges (Patent Documents 3 and 4), Prism
Ballast (Patent Documents 5 and 6) and Double Slab Off (Patent
Documents 7 and 8). Further, in the multifocal contact lens, the
power of the lens is distributed so that a distance vision area for
distance vision and a near vision area for near vision are arranged
in the optical portion (Patent Document 9). Further, multifocal
toric contact lenses combining a toric surface for correcting
astigmatism and a multifocal power for correcting presbyopia in the
optical portion has also been developed (Patent Documents 10 and
11).
PRIOR ART DOCUMENT
Patent Document
[0004] [Patent Document 1] Japanese Patent Laid-Open Publication
No. 1984-53812 [0005] [Patent Document 2] Published Japanese
Translation of PCT International Application No. 2005-502072 [0006]
[Patent Document 3] Published Japanese Translation of PCT
International Application No. 2001-522065 [0007] [Patent Document
4] Published Japanese Translation of PCT International Application
No. 2005-534985 [0008] [Patent Document 5] Published Japanese
Translation of PCT International Application No. 2004-506925 [0009]
[Patent Document 6] Published Japanese Translation of PCT
International Application No. 2006-529029 [0010] [Patent Document
7] WO 2009/139021 [0011] [Patent Document 8] Published Japanese
Translation of PCT International Application No. 2007-538288 [0012]
[Patent Document 9] Japanese Patent Laid-Open Publication No.
1997-15541 [0013] [Patent Document 10] WO 2011/061790
[0014] [Patent Document 11] Published Japanese Translation of PCT
International Application No. 2005-534966
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0015] Incidentally, when trying to deploy an axis stabilizing
mechanism by combining toric with a multifocal contact lens,
further when handling a toric contact lens which is not multi-focal
(this lens is also called a (multi-focal) toric contact lens), the
following problem occurs. In a case of a multifocal toric contact
lens with truncation (example: prior documents 1 and 2), although
it is suitable as a special order for wearers with unique eyes
because of its characteristic shape, it is not suitable for mass
production. Further, compared with a simple spherical lens, an
entire lens has a distorted shape, and foreign body feeling
(deterioration of wearing feeling) inevitably occurs.
[0016] In the case of a multifocal toric contact lens having a
ridge (for example, prior art documents 3 and 4), a raised ridge at
a lower part of the lens is engaged with a lower eyelid and
positional stability and directivity can be obtained. However, the
degree of engagement between the lower eyelid and the ridge is not
suitable for mass production because there are individual
differences in the lower eyelid. Further, the upper eyelid more
easily hits a ridge convex shape, and the wearing feeling is
inferior to the spherical lens.
[0017] In the case of a multifocal toric contact lens with a prism
ballast (for example, prior art documents 5, 6 and 9), the prism is
formed over the entire lens, and therefore a thickness is increased
from an upper end part of the lens to a lower end part of the lens,
and the prism also remains in the optical portion in which the
multifocal is formed. As a result, the prism of the optical portion
acts as a hindrance factor for correcting the distance vision area
and correcting the near vision area, and in order to solve this
problem, more complicated optical design is required. Further,
since ballast is formed on a part of the lens, the lens more easily
falls downward than a usual lens. In this case, centering of the
lens becomes difficult, and in order to ensure centering, the
necessity of machining to obtain a balance is generated by scraping
off somewhere in the lens to make it thin. When processed, the
entire lens has a distorted shape as compared with a spherical
lens, resulting in a foreign body feeling.
[0018] In the case of the multifocal toric contact lens with double
slab off (for example, prior art documents 10 and 11), the lens has
bilateral symmetry and vertical symmetry, and therefore centering
by the wearer is easy to be obtained, bifocal optical design is
easy to be exhibited, and no prism is formed in the lens, and
therefore it is possible to expect an effect of not allowing the
hindrance factor to occur in the optical design of the distance
vison area or the near vision area. However, in order to secure
axis stability with double slab off without ballast, it is
necessary to distribute the thickness in such a way that a thick
region is formed so as to emphasize a peripheral portion, or a thin
region of the peripheral portion is expanded, thus distorting a
lens shape compared with a spherical lens. Further, in a case of a
thickness design in which astigmatism correction is provided on the
optical portion of the front surface and double slab off is
provided on the peripheral portion of the front surface, and
multifocal is provided on the optical portion on the rear surface
(for example: prior document 11), the lens has optical properties
aiming at different effects on the front and rear surfaces.
Therefore, a lens specializing in optical design and processing can
be provided. However, each of the front and rear surfaces requires
a characteristic shape, therefore as a result, the entire lens has
a distorted shape, and the wearing feeling is deteriorated as
compared with a spherical lens.
[0019] Thus, it is requested to develop the (Multifocal) toric
contact lens capable of exhibiting bifocal optical design to the
maximum and correcting astigmatism fully effectively, and in
addition, capable of obtaining good wearing feeling.
[0020] In view of the above-described circumstance, an object of
the present invention is to provide a contact lens capable of
correcting astigmatism fully effectively (preferably correcting
presbyopia in addition to correcting astigmatism), and a method for
manufacturing the same. Also, an object of the present invention is
to provide a contact lens capable of providing excellent wearing
feeling in addition to improving centering performance and axis
stability, and a method for manufacturing the same.
Means for Solving the Problem
[0021] In order to solve such a problem, the inventors of the
present invention have found an invention having the following
configuration. Namely, there is provided a contact lens having a
convex front surface and a concave rear surface,
[0022] the front surface being divided into an optical portion, an
edge joining the front and rear surfaces, a first smoothing portion
arranged on an outer periphery of the optical portion, a peripheral
portion arranged on an outer periphery of the first smoothing
portion, and a second smoothing portion connecting the peripheral
portion and the edge,
[0023] the front surface having mirror image symmetry with respect
to a vertical meridian as a boundary extending from an upper end of
the lens to a lower end of the lens passing through a midpoint of
the lens, and having mirror image symmetry also with respect to the
horizontal meridian perpendicular to the vertical meridian at the
lens midpoint,
[0024] the peripheral portion being arranged to include the
horizontal meridian, and configured of:
[0025] a first peripheral portion arranged to include the
horizontal meridian and having a shape so as to maximize a
thickness of the contact lens on the horizontal meridian,
[0026] a second peripheral portion arranged to include the vertical
meridian and having a shape so as to minimize the thickness of the
contact lens on the vertical meridian,
[0027] a first peripheral auxiliary portion which is a portion
adjacent to the first peripheral portion, having a surface shape so
as to keep the thickness of the contact lens constant; and
[0028] an inclined portion which is a portion connecting the first
peripheral auxiliary portion and the second peripheral portion to
form a continuous surface, and having a surface shape that changes
the thickness of the contact lens.
[0029] According to the present invention, an entire lens has
mirror image symmetry with respect to the vertical direction and
the horizontal direction, and therefore the lens is more easily to
be arranged in the cornea center during wearing. By improving the
centering performance of the lens, it is possible to improve
accuracy of correcting presbyopia in the distance vision area and
the near vision area allocated to a desired area in the optical
portion.
[0030] Further, since the first peripheral portion having a largest
thickness is arranged so as to include the horizontal meridian, and
the second peripheral portion having a smallest thickness is
arranged so as to include the vertical meridian perpendicular to
the horizontal meridian, the first peripheral portion is pushed out
to the ear/nose side by the eyelid for every blinking. Further,
since the first peripheral auxiliary portion having the surface
with constant thickness is adjacent to the first peripheral
portion, it is possible to help the eyelid move to the first
peripheral portion. As a result, axis stability is improved, and in
the case of a multifocal lens, good presbyopia correction can be
obtained even in an elliptical optical portion.
[0031] Then, the first smoothing portion smoothly connects the
optical portion (for example, the elliptical optical portion formed
for correcting astigmatism and having a long axis in a horizontal
direction), and the peripheral portion formed for axis stability
(for example, elliptical and annular peripheral portion in
correspondence with the optical portion), and the second smoothing
portion smoothly connects the elliptical annular peripheral portion
formed for axis stability and a perfect circular edge, and the
inclined portion smoothly connects the first peripheral auxiliary
portion and the second peripheral portion having different heights
(thicknesses). In this way, centering performance and axis
stability are improved and a good wearing feeling is obtained.
[0032] Second, a radial width of the peripheral portion is
constant, and third, a surface area ratio of the peripheral portion
to the front surface is 1:99 to 10:90. This makes it possible to
fully secure a region of the second smoothing portion surrounded by
the peripheral portion and the edge, without narrowing the areas
for correcting presbyopia and correcting astigmatism, while
ensuring the axis stability although the peripheral stability is
kept to a minimum. As a result, the difference from the spherical
lens becomes small, and the wearing feeling is improved. Further,
by simultaneously providing the optical design and the axis
stabilizing mechanism having both of correcting presbyopia and
correcting astigmatism on the front surface of the lens, an
aspherical shape that matches a cornea can be provided to the lens
rear surface, which greatly affects the wearing feeling.
[0033] Fourth, the thickness as viewed in the radial direction is
constant in the first peripheral portion, fifth, the thickness as
viewed in the circumferential direction is decreased in the first
peripheral portion when rotating from the horizontal meridian to
the vertical meridian, and sixth, the thickness as viewed in the
radial direction is constant in the second peripheral portion, and
seventh, a radial width of the first peripheral auxiliary portion
is decreased when rotating from the horizontal meridian to the
vertical meridian, and a radial width of the second peripheral
portion is increased when rotating from the horizontal meridian to
the vertical meridian, and the boundary between the inclined
portion and the second peripheral portion is parallel to the
horizontal meridian. As a result, the centering performance and the
axis stability are further improved, and good wearing feeling is
also obtained. The radial width of the first peripheral auxiliary
portion may be a configuration unit that is decreased when rotating
from the horizontal meridian to the vertical meridian. Also, the
radial width of the second peripheral portion may be a
configuration unit that is increased when rotating from the
horizontal meridian to the vertical meridian. Further, the boundary
between the inclined portion and the second peripheral portion may
be a configuration unit that is parallel to the horizontal
meridian.
[0034] Eighth, by forming the optical portion by a toroidal
surface, it is possible to provide a toric contact lens having an
astigmatism correcting function.
[0035] Ninth, in the optical portion, regions of different powers
are arranged in an elliptical shape, including a distance vision
portion for a distance vision arranged at a center of the optical
portion, and a first intermediate portion arranged on the outer
periphery of the distance vision portion and having a power
distribution continuously increasing from the power of the distance
vision portion, and a near vision portion for a near vision
arranged on the outer periphery of the first intermediate portion.
Further, tenth, in the optical portion, regions of different powers
are arranged in an elliptical shape, including the near vision
portion arranged at a center of the optical portion, a second
intermediate portion arranged on the outer periphery of the near
vision portion and having a power distribution continuously
decreasing from the power of the near vision portion, and a
distance vision portion arranged on the outer periphery of the
second intermediate portion. This makes it possible to provide a
multi focal contact lens.
[0036] Eleventh, by using a hydrogel or a silicone hydrogel as a
lens material, it is possible to provide a soft contact lens having
a good wearing feeling and provide a silicone hydrogel contact lens
having high oxygen permeability.
[0037] Twelfth, by setting the center thickness in the optical
portion to be in a range of 0.05 to 0.20 mm, the wearing feeling
can be improved.
[0038] Thirteenth, within a predetermined rotation angle range of
the rotation from the horizontal meridian to the vertical meridian
in the peripheral portion, the first peripheral auxiliary portion
is arranged on one side of an inner peripheral side or an outer
peripheral side, and the inclined portion is arranged on the other
side of the inner peripheral side or the outer peripheral side, so
that the both are made to coexist. In addition, fourteenth, the
first peripheral auxiliary portion is arranged on the inner
peripheral side and the inclined portion is arranged on the outer
peripheral side so that the both are made to coexist. Exquisite
axis stability is improved favorably in the region of the
peripheral portion when rotating from the horizontal meridian to
the vertical meridian, due to coexistence of the first peripheral
auxiliary portion and the inclined portion, in the detailed
configuration as described above.
[0039] Fifteenth, a shape of the peripheral portion is made to be
elliptical and annular having a long axis in the horizontal
direction. This is the configuration as an example. Thereby, it is
possible to secure a wide second peripheral portion on the vertical
meridian.
[0040] Sixteenth, there is provided a method for manufacturing a
contact lens using a cast mold manufacturing method, the contact
lens having a convex front surface and a concave rear surface,
[0041] the front surface being divided into an optical portion, an
edge joining the front and rear surfaces, a first smoothing portion
arranged on an outer periphery of the optical portion, a peripheral
portion arranged on an outer periphery of the first smoothing
portion, and a second smoothing portion connecting the peripheral
portion and the edge,
[0042] the front surface having mirror image symmetry with respect
to a vertical meridian as a boundary extending from an upper end of
the lens to a lower end of the lens passing through a midpoint of
the lens, and having mirror image symmetry also with respect to the
horizontal meridian perpendicular to the vertical meridian at the
lens midpoint,
[0043] the peripheral portion being arranged to include the
horizontal meridian, and configured of:
[0044] a first peripheral portion arranged to include the
horizontal meridian and having a shape so as to maximize a
thickness of the contact lens on the horizontal meridian,
[0045] a second peripheral portion arranged to include the vertical
meridian and having a shape so as to minimize the thickness of the
contact lens on the vertical meridian,
[0046] a first peripheral auxiliary portion which is a portion
adjacent to the first peripheral portion, having a surface shape so
as to keep the thickness of the contact lens constant; and
[0047] an inclined portion which is a portion connecting the first
peripheral auxiliary portion and the second peripheral portion to
form a continuous surface, and having a surface shape that changes
the thickness of the contact lens.
Advantage of the Invention
[0048] According to the contact lens of the present invention, good
wearing feeling is obtained together with improved centering
performance and axis stability as compared with a conventional
contact lens. As a result, the bifocal optical design can be
exhibited to the maximum and astigmatism can be corrected fully
effectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1A is a view for explaining a configuration of a
contact lens according to an embodiment of the present invention,
and is a front view of the same contact lens.
[0050] FIG. 1B is a view for explaining a configuration of a
contact lens according to an embodiment of the present invention,
and is side view of the same contact lens.
[0051] FIG. 2A is a view for explaining a power distribution of an
optical portion in the contact lens, and is a front view of the
optical portion in the same contact lens.
[0052] FIG. 2B is a view for explaining the power distribution in
the optical portion of the contact lens, and is a graph showing a
power distribution state of the lens at OA position.
[0053] FIG. 3 is a front view enlarging the vicinity of 0.degree.
to 90.degree. of the contact lens.
[0054] FIG. 4 is a cross-sectional view showing how to define a
thickness of the contact lens.
[0055] FIG. 5A is a view for explaining a cross section of the lens
at a predetermined angle of the contact lens, and is a front view
enlarging the vicinity of 0.degree. to 90.degree. of the same
contact lens.
[0056] FIG. 5B is a view for explaining a lens cross section at a
predetermined angle of the contact lens, and is a schematic diagram
showing a lens cross section at an angle shown in FIG. 5A.
[0057] FIG. 6A is a view for explaining a thickness distribution of
the contact lens, and is a front view of the same contact lens.
[0058] FIG. 6B is a view for explaining the thickness distribution
of the contact lens, and is a thickness transition diagram on a
circumference M.
[0059] FIG. 6C is a view for explaining the thickness distribution
of the contact lens, and is a thickness transition diagram on the
circumference N.
[0060] FIG. 7 is a view for explaining the thickness of the
peripheral portion of the contact lens, and is a front view of the
same contact lens.
[0061] FIG. 8A is a view for explaining the thickness of the
peripheral portion of the contact lens, and is a perspective view
in which the vicinity of 0.degree. to 50.degree. is cut out.
[0062] FIG. 8B is a view for explaining the thickness of the
peripheral portion of the contact lens, and is a perspective view
in which the vicinity of 50.degree. to 70.degree. is cut out.
[0063] FIG. 8C is a view for explaining the thickness of the
peripheral portion of the contact lens, and is a perspective view
in which the vicinity of 70.degree. to 90.degree. is cut out.
[0064] FIG. 8D is a view for explaining the thickness of the
peripheral portion of the contact lens, and is a perspective view
in which the vicinity of 50.degree. to 90.degree. is cut out.
[0065] FIG. 9A is a view for explaining a lens cross section along
a horizontal meridian near a lens upper end portion of the contact
lens, and is a front view of the same contact lens viewed from a
front side.
[0066] FIG. 9B is a view for explaining the lens cross section
along the horizontal meridian near the lens upper end portion of
the contact lens, and is a view showing a thickness variation
profile of cutting planes CP 0, CP 100 and CP 200 shown in FIG.
9A.
[0067] FIG. 9C is a view for explaining a lens cross section along
the horizontal meridian near the lens upper end portion of the
contact lens, and is an enlarged view showing an inside of a
two-dot chain line L of FIG. 9A.
[0068] FIG. 9D is a view for explaining the lens cross section
along the horizontal meridian near the lens upper end portion of
the contact lens, and is a view showing a thickness variation of
the cutting planes CP 20 to CP 120 in FIG. 9C.
DETAILED DESCRIPTION OF THE INVENTION
[0069] The above-described objects, features and advantages of the
present invention will become more apparent from the following
detailed description of embodiments and examples with reference to
the drawings. Embodiments of the present invention will be
described hereafter, with reference to the drawings. It should be
noted that the present invention is not limited to the following
examples. Further, in the present invention, when dividing the
configuration largely, "," is added as a normal punctuation mark,
and when dividing a small configuration, "," is added as a
punctuation mark. Moreover, FIG. 1a and Table 2a are mainly
represented like FIG. 1A and Table 2(a). Moreover, in the present
invention, "smoothly connecting (combining, joining, reducing
thickness, etc.)" means that objects to be connected together form
one continuous surface, and means that discontinuous sharp
irregularities do not appear suddenly. Further, in the present
invention, "constant thickness" means that the thickness of the
contact lens is equal within a predetermined region (for example,
in-plane), and also referred to as a uniform thickness and
flat.
[0070] As shown in FIG. 1A, the contact lens 10 (sometimes simply
referred to as a lens) is formed by a convex front surface (also
referred to as a front curve) 12 and a concave rear surface (also
referred to as a base curve) 14. The edge 16 joins the front curve
12 and the base curve 14.
[0071] An optical portion 18 for defining a refractive power for
correcting presbyopia and astigmatism, and a double slab off 20
having an axis stabilization mechanism, are provided to the front
curve 12 of the contact lens 10. The base curve 14 is formed in a
rotationally symmetrical shape having a multi-step curve matching a
corneal shape of a wearer. Namely, the shape of the base curve 14
is the same shape (concentric circle) even if it is cut in an
arbitrary longitudinal (diameter) direction (described later).
Parameters of the contact lens 10 include, base curve: 8.6 mm,
optical center thickness: 0.09 mm, total diameter: 14.2 mm, myopic
power: -3.00 D, astigmatic power: -0.75 D, axis: 180.degree. and
addition power: +1.5 D. As shown in FIG. 1B, the myopic power is
determined by curvature R1 of the front curve 12 and curvature R2
of the base curve 14.
[0072] Returning to FIG. 1A, the optical portion 18 has an
elliptical toroidal surface (also referred to as a toric surface)
in which a horizontal direction is a long axis (main axis) and a
vertical direction is a short axis (minor axis). Namely, in order
to correct astigmatism, a curved surface (toroidal surface) is
formed so that a curvature radius is different between two
orthogonal axes (two axes of major axis (long axis) and minor axis
(short axis) hereafter unless otherwise specified).
[0073] In a case of this example, due to 180.degree. axis, a
curvature of the main axis (long axis) on the horizontal meridian
24 is greater than a curvature of the minor axis (short axis) on
the vertical meridian 22. The length of the axis of the ellipse or
the angle of the ellipse is varied according to a desired
refractive power.
[0074] Here, the meridian means an intersecting line of the lens
surface (the front curve 12 or the base curve 14) and a plane
including a lens center axis, and types of the meridians include
vertical meridian 22, horizontal meridian 24 and angular meridian
26, any one of which are indicated by one-dot chain lines. The
vertical meridian 22 is a meridian passing through the lens upper
end portion 28 and the lens lower end portion 30 and the lens
midpoint O, and the horizontal meridian 24 is a meridian
perpendicular to the vertical meridian 22 and passing through the
lens midpoint O. The angular meridian 26 is a meridian on an
arbitrary angle (angle .theta. in this case) centered on the lens
midpoint O, and can also be called a line extending radially from
the lens midpoint O toward the edge 16. Further, the radial
direction is a direction radially extending from the lens midpoint
O to an arbitrary distance. The circumferential direction is a
direction of a circumference centered on the lens midpoint O, and
in a case of this example, a locus indicated by an arc in a fan
shape surrounded by the lens midpoint O, the horizontal meridian 24
and the angular meridian 26 can also be called the circumferential
direction.
[0075] The front curve 12 has mirror image symmetry with respect to
the vertical meridian 22 as a boundary. Namely, a right half and a
left half have the same shape, bordering vertical meridian 22
passing through the lens midpoint O. The front curve 12 also has
mirror image symmetry with respect to the horizontal meridian 24 as
a boundary. Namely, the upper half and the lower half have the same
shape bordering the horizontal meridian 24 passing through the lens
midpoint O. In this way, since the entire lens has the mirror image
symmetry with respect to the vertical direction and the horizontal
direction, the lens is more easily to be arranged in the cornea
center during wearing. Due to improvement of the centering
performance of the lens, it is possible to improve the accuracy of
correcting presbyopia in the distance vision area and the near
vision area allocated to desired areas in the optical portion.
Further, it is also possible to use the lens without distinction
between left and right eyes. Further, even when the lens carries
out 180.degree. rotation on the eye, axis stability is
obtained.
[0076] In the following description, the angle of the contact lens
10 is determined based on wearing the contact lens 10 on the right
eye, and is defined as follows: the lens upper end portion 28 is at
a position of 90.degree. (on the eyebrow side), the lens lower end
portion 30 is at a position of 270.degree. (on the jaw side), the
nose side of the directions parallel to the horizontal meridian 24
is at a position of 0.degree., and the opposite side (ear side) is
at a position of 180.degree..
[0077] Further, the contact lens 10 has mirror image symmetry with
respect to the vertical meridian 22 and horizontal meridian 24.
Therefore, the cross section of a lens from 0.degree. to 90.degree.
(counterclockwise) has the same shape as the cross section of a
lens from 180.degree. to 90.degree. (clockwise), from 180.degree.
to 270.degree. (counterclockwise), and from 360.degree. (0.degree.)
to 270.degree. (clockwise). As an example, the cross section of a
lens from 0.degree. to 50.degree. (counterclockwise) has the same
shape as the cross section of a lens from 180.degree. to
130.degree. (clockwise), from 180.degree. to 230.degree.
(counterclockwise), and from 0.degree. to 310.degree. (clockwise),
and the cross section of a lens from 50.degree. to 70.degree.
(counterclockwise) has the same shape as the cross section of a
lens from 130.degree. to 110.degree. (clockwise), from 230.degree.
to 250.degree. (counterclockwise), and from 310.degree. to
290.degree. (clockwise), and the cross section of a lens from
70.degree. to 90.degree. (counterclockwise) has the same shape as
the cross section of a lens from 110.degree. to 90.degree.
(clockwise), from 250.degree. to 270.degree. (counterclockwise) and
from 290.degree. to 270.degree. (clockwise).
[0078] With reference to FIG. 2A, in the contact lens 10, the
distance vision portion 32 for distance vision is arranged at the
center of the optical portion 18, an intermediate portion 34 having
a power distribution continuously increasing from the power of the
distance vision portion is arranged around the distance vision
portion 32, and the near vision portion 36 for near vision arranged
around the first intermediate portion 34, is arranged as an
outermost periphery of the optical portion 18.
[0079] FIG. 2B shows a power distribution state of the lens at OA
position of FIG. 2A. In these figures, the horizontal axis shows a
distance.times.(mm) from the lens midpoint O, and the vertical axis
shows a power (D). Due to having the mirror image symmetry with
respect to the horizontal meridian 24, the same curve is drawn for
the power distribution state of the lens at O-B position shown in
FIG. 2A and the power distribution state of the lens at O-A
position.
[0080] With reference to FIG. 3, the double slab off 20 is divided
into a first smoothing portion 38 arranged on the outer periphery
of the optical portion 18, an elliptical peripheral portion 40
arranged on the outer periphery of the first smoothing portion 38,
and a second smoothing portion 42 connecting the peripheral portion
40 and the edge 16.
[0081] The first smoothing portion 38 smoothly connects the optical
portion 18 that is elliptical as a result of correcting
astigmatism, and the peripheral portion 40 which is an ellipse and
annular (explanation for "annular" is omitted thereafter). Thereby,
unnecessary friction does not occur between the lens touched during
wearing and the upper and lower eyelids, and a foreign body feeling
(deterioration in wearing feeling) hardly occurs. Further, the
first smoothing portion 38 functions as a buffer area, and
therefore even with any refractive power, the elliptical equality
of the peripheral portion 40 is secured. When the axis of the
contact lens 10 is 180.degree., it does not matter if there is a
matching between the ratio of the length of the major axis to the
length of the minor axis of the ellipse in the optical portion 18,
and the ratio of the length of the major axis on the horizontal
meridian 24 to the length of the minor axis on the vertical
meridian of the ellipse in the peripheral portion 40.
[0082] The width of the peripheral portion 40 is constant at an any
angle. Further, the surface area ratio of the peripheral portion 40
with respect to the front curve 12 is 1:99 to 10:90. In this way,
the axis stability is secured while the peripheral portion 40 is
minimized, and it is possible to sufficiently secure the region of
the second smoothing portion 42 surrounded by the peripheral
portion 40 and the edge 16 without narrowing the areas for
correcting presbyopia and correcting astigmatism. As a result, the
difference from the spherical lens becomes small, and the wearing
feeling is improved. Further, by simultaneously providing the
optical design having both presbyopia correction and astigmatic
correction and the axis stabilizing mechanism on the front surface
of the lens, an aspherical shape that matches the cornea can be
provided on the rear surface of the lens, which greatly affects the
wearing feeling. The peripheral portion 40 will be described later
in detail.
[0083] The second smoothing portion 42 smoothly joins the
elliptical peripheral portion 40 and the perfect circular edge 16.
Since the second smoothing portion 42 functions as a buffer region,
equality of the peripheral portion 40 of the ellipse and equality
of the perfect circular edge 16 are secured. Further, as a result
of a smooth joint, unnecessary friction between the lenses touched
during wearing and the upper and lower eyelids is reduced, and
foreign body feeling hardly occurs.
[0084] Next, the thickness of the contact lens 10 will be
described. As shown in FIG. 4, the thickness T of the contact lens
10 (hereinafter simply referred to as a thickness) is defined as a
distance from an arbitrary point on the base curve 14 to a point
where a perpendicular line orthogonal to a tangent to this
arbitrary point intersects with the front curve 12. The thickness T
in the optical portion 18 is regulated in accordance with the
degree for correcting visual acuity. On the other hand, the
thickness T in the first smoothing portion 38, the peripheral
portion 40 and the second smoothing portion 42 excepting the
optical portion 18 can be changed to a desired value.
[0085] When looking at the entire contact lens 10, the thickness of
the lens in a radial direction becomes maximum in the peripheral
portion 40 at any angle. With reference to FIGS. 5(a) and (b), in
the lens cross section from 0.degree. and 30.degree., the thickness
is gradually increased from the lens midpoint O to point m1 through
the optical portion 18 and the first smoothing portion 38, and the
thickness is gradually decreased from the point n1 to the edge 16
through the second smoothing portion 42 (that is, "continuously
decreases", and the same thereafter). Further, the thickness from
point m1 to point n1 is uniform. Namely, the thickness of the
peripheral portion 40 becomes maximum at point m1 (point n1). In
the lens cross section of 50.degree., the thickness is gradually
increased from the lens midpoint O to point m2 through the optical
portion 18 and the first smoothing portion 38, and the thickness is
gradually decreased from point n2 to the edge 16 through the second
smoothing portion 42. Further, the thickness T is uniform from
point m2 to point n2, and at this time, the thickness of the
peripheral portion 40 becomes maximum. In the lens cross section of
70.degree., the thickness is gradually increased from the lens
midpoint O to point m3 through the optical portion 18 and the first
smoothing portion 38. After the thickness reaches the maximum at
point m3, the thickness is gradually decreased to the edge 16
through point n3 and the second smoothing portion 42. In the cross
section of the lens of 90.degree., the thickness T is gradually
increased from the lens midpoint to point m4 through the optical
portion 18 and the first smoothing portion 38, and the thickness T
is gradually decreased from point n4 to the edge 16 through the
second smoothing portion 42. Further, the thickness is uniform from
point m4 to point n4. Namely, the thickness of the peripheral
portion 40 becomes maximum at point m4 (point n4). In this way, the
thickness is increased from the lens midpoint O to the peripheral
portion 40 through the optical portion 18 and the first smoothing
portion 38, and the thickness T is gradually decreased from the
peripheral portion 40 to the edge 16 through the second smoothing
portion 42.
[0086] Particularly in this embodiment, the thickness of the
peripheral portion 40 has a large characteristic. Details will be
described below. The thickness of the peripheral portion 40 in a
circumferential direction is different for each area classified at
a prescribed angle. FIGS. 6B and 6C are schematic views showing the
thickness distribution of the peripheral portion 40 at a
predetermined angle shown in FIG. 6A, and the degree of the
thickness distribution is expressed as shown by the notation pf
Table 1. The thickness distribution viewed throughout the lens is
shown in FIG. 7 to be described later.
[0087] As shown in FIG. 7, the peripheral portion 40 is composed of
a first peripheral portion 44, a second peripheral portion 46, a
first peripheral auxiliary portion 48, and an inclined portion 50.
The first peripheral portion 44 is a portion arranged so as to
include the horizontal meridian 24 (as an example, so as to
straddle) the horizontal meridian 24, and having a shape maximizing
the thickness of the contact lens 10 on the horizontal meridian 24.
The second peripheral portion 46 is a portion arranged so as to
include the vertical meridian 22 (as an example, so as to straddle
the vertical meridian 22), and having a shape minimizing the
thickness of the contact lens 10 on the vertical meridian 22. The
first peripheral auxiliary portion 48 is a portion adjacent to the
first peripheral portion 44, and having a surface shape for keeping
the thickness of the contact lens 10 constant. The inclined portion
50 is a portion for making a continuous surface by connecting the
first peripheral auxiliary portion 48 and the second peripheral
portion 46, and having a surface shape of varying the thickness of
the contact lens 10. The thickness of the first peripheral portion
44 viewed in the radial direction is constant, and the thickness of
the first peripheral portion 44 viewed in the circumferential
direction is decreased when rotating from the horizontal meridian
24 to the vertical meridian 22. The thickness of the second
peripheral portion 46 is constant, and a radial width of the first
peripheral auxiliary portion 48 is decreased when rotating from the
horizontal meridian 24 to the vertical meridian 22, and a radial
width of the second peripheral portion 46 is increased when
rotating from the horizontal meridian 24 to the vertical meridian
22. The boundary between the inclined portion 50 and the second
peripheral portion 46 is parallel to the horizontal meridian
24.
[0088] Regarding the thickness of the circumference M on the inner
side of the peripheral portion 40 (hereinafter also simply referred
to as the inner circumferential side or the inner side), as shown
in FIG. 7 and FIG. 6B, thickness Tma from point m1 (0.degree.) to
point m2 (50.degree.=predetermined rotation angle .theta.1) is
gradually decreased, thickness Tmb from point m2) (50.degree.) to
point m3 (70.degree.=predetermined rotation angle .theta.2) is
equal, and thickness Tmc from point m3 (70.degree.) to point m4
(90.degree.) is gradually decreased. Further, regarding the
thickness of the circumference N on the outer side of the
peripheral portion 40 (hereinafter also simply referred to as the
outer circumferential side or the outer side), as shown in FIG. 7
and FIG. 6C, thickness Tna from point n1 (0.degree. to point n2
(50.degree.=predetermined rotation angle .theta.1) is gradually
decreased, thickness Tnb from point n2 (50.degree.) to point n3
(70.degree.=predetermined rotation angle .theta.2) is gradually
decreased, and thickness Tnc from point n3 (70.degree.) to point n4
(90.degree.) is equal. As a result, thickness T of the peripheral
portion 40 becomes maximum at a position of 0.degree., whereas
thickness T becomes minimum at a position of 90.degree..
[0089] Here, the difference between FIGS. 6(b) and (c) will become
clear by referring to FIG. 7. For example, the circumference M
inside of the peripheral portion 40 (FIG. 6B), is a first
peripheral auxiliary portion 48 in which thickness T is constant
from point m2 (50.degree.) to point m3 (70.degree.). Meanwhile, on
the circumference N (FIG. 6C) which is the outside of the
peripheral portion 40, only one point in the first peripheral
auxiliary portion 48 exists only at point n (50.degree.), and
instead the inclined portion 50 is present. In addition, on the
circumference M inside of the peripheral portion 40 (FIG. 6B), only
one point in the second peripheral portion 46 is present at only
point m4 (90.degree.), but on the circumference N which is the
outside of the peripheral portion 40 (FIG. 6C), an area from point
n3 (70.degree.) to point n4 (90.degree.)is the second peripheral
portion 46. At a point m2 (50.degree.) on the circumference M
inside of the peripheral portion 40, it is assumed that the first
peripheral portion 44 and the first peripheral auxiliary portion 48
coexist. The same is applied to other boundaries. However, it may
be defined that only one of them is present, from a viewpoint of
correctly expressing the contents.
[0090] In FIGS. 6B and 6C, it is explained that the thickness is
gradually increased (or the thickness is gradually decreased).
However, it is possible to adopt any shape as long as the thickness
is increased (or decreased), and for example it is also possible to
adopt an n th-order function, an exponential function or a
logarithmic function, as long as the thickness is increased or
decreased by a linear function as shown in FIGS. 6B and 6C.
[0091] The region at 0.degree. to 50.degree. indicated by grid in
FIG. 7 is the first peripheral portion 44, and FIG. 8A shows a
schematic diagram of the peripheral portion 40 cut out by a range
of 0.degree. to 50.degree.. The first peripheral portion 44 has a
uniform thickness in a radial direction from the horizontal
meridian 24 (point m1, point n1) to the boundary of the first
peripheral auxiliary portion 48 (point m2, point n2). Namely,
thickness Tma at point m1 and thickness Tna at point n1 are the
same height, and thickness Tma at point m2 and thickness Tna at
point n2 are the same height. The thickness of the first peripheral
portion 44 also becomes maximum on the 0.degree. angular meridian
26 (on the horizontal meridian 24), and becomes minimum on the
50.degree. angular meridian 26. Further, width Wa of the first
peripheral portion 44 has the same distance at any angle. Namely,
the distance from point m1 to point n1 is equal to the distance
from point m2 to point n2. In this way, the first peripheral
portion 44 with its thickness maximized in the peripheral portion
40 is arranged so as to straddle the horizontal meridian 24, with
its thickness smoothly decreased from 0.degree. to 50.degree. and
has a uniform thickness on width Wa at any angle. By arranging the
first peripheral portion 44 having the maximum thickness on the
horizontal meridian 24, the contact lens 10 is pushed out to the
upper eyelid or the lower eyelid and is rotated, and the first
peripheral portion 44 moves to the ear side or the nose side.
Further, by contacting the eyelid with the first peripheral portion
44 having a uniform thickness in the radial direction, that is, a
flat (planar) surface by planes, horizontal directivity is given to
the contact lens 10 for every blinking. The maximum thickness of
the first peripheral portion 44 can be appropriately set within a
range that does not interfere with wearing the contact lens 10.
However, it is preferably less than 0.4 mm, and more preferably 0.3
mm or less, in view of wearing feeling and the like.
[0092] The region indicated by vertical stripes at 50.degree. to
70.degree. in FIG. 7 is the first peripheral auxiliary portion 48,
and FIG. 8B shows a schematic diagram of the peripheral portion 40
cut out by a range of 50.degree. to 70.degree.. The first
peripheral auxiliary portion 48 has a flat thickness (the same
thickness) from the boundary (point m2, point n2) of the first
peripheral portion 44 to the end point (point m3) of the inclined
portion 50. Namely, thickness Tmb at point m2, thickness Tmb at
point m3 and thickness Tnb at point n2 are the same height.
Further, width Wb of the first peripheral auxiliary portion 48 is
shortened in a range of 50.degree. to 70.degree.. Namely, width Wb
is longest at 50.degree. and width Wb is shortest at 70.degree.. In
the cutting plane passing through an arbitrary point a in the range
of 50.degree. to 70.degree., there are thickness Tmb on the
circumference M, thickness Tnb on the circumference N, and
thickness Ta on the point a. At this time, thickness Ta and
thickness Tmb are the same thickness (equal thickness), and
thickness Tnb is lower than thickness Tmb (Ta). In this way, the
flat first peripheral auxiliary portion 48 is located between the
inclined portion 50 and the first peripheral portion 44. Thereby,
the first peripheral auxiliary portion 48 functions as a buffer
area when the upper and lower eyelids move from the first
peripheral portion 44 to the inclined portion 50 or from the
inclined portion 50 to the first peripheral portion 44, and smooth
axis stability can be provided. It should be noted that the first
peripheral auxiliary portion 48 mentioned here has a surface shape,
and it is assumed that the thickness is constant in the radial
direction and the circumferential direction in the plane (the same
thickness anywhere in the plane).
[0093] The region indicated by horizontal stripes at 70.degree. to
90.degree. in FIG. 7 is the second peripheral portion 46, and FIG.
8C shows a schematic diagram of the peripheral portion 40 cut out
by a range of 70.degree. to 90.degree.. The second peripheral
portion 46 has a flat thickness from the end point (point n3) of
the inclined portion 50 to the vertical meridian 22 (point m4,
point n4). Namely, thickness Tmc at point m4, thickness Tnc at
point n3, and thickness Tnc at point n4 have the same height.
Further, width Wc in the second peripheral portion 46 widens from
70.degree. to 90.degree.. Namely, width Wc is shortest at
70.degree. and is longest at 90.degree.. There are thickness Tmc on
the circumference M, thickness Tnc on the circumference N, and
thickness T.beta. on the point .beta., in a cutting plane passing
through arbitrary point .beta. in the range of 70.degree. to
90.degree.. At this time, thickness T.beta. and thickness Tnc have
the same, and thickness Tmc is higher than thickness Tnc (T.beta.).
In this way, the second peripheral portion 46 having a thinnest
thickness in the peripheral portion 40 is arranged to straddle the
vertical meridian 22 as a flat thick surface having a distance in
the horizontal direction. By arranging the second peripheral
portion 46 on the vertical meridian 22 orthogonal to the horizontal
meridian 24, the contact lens 10 moves for every blinking so that
the second peripheral portion 46 enters the upper eyelid or the
lower eyelid. The second peripheral portion 46 mentioned here is a
uniform thickness portion including the portion on the vertical
meridian 22, otherwise, a linear portion on the vertical meridian
22, on the assumption that the portion on the vertical meridian 22
has a shape having a minimum thickness.
[0094] Incidentally, in the present embodiment, the shape of the
peripheral portion 40 is an elliptical annular shape whose major
axis is the direction of the horizontal meridian 24. As a result,
it is possible to ensure a wide second peripheral portion 46 on the
vertical meridian 22. Further, the minimum thickness of the second
peripheral portion 46 can be appropriately set within a range that
does not interfere with wearing the contact lens 10, and is
preferably set to a value exceeding 0.10 mm, and more preferably to
be 0.15 mm or more, in order to prevent the axis from continuing
unstable rotating.
[0095] In FIG. 7, the region indicated by oblique lines at
50.degree. to 90.degree. is the inclined portion 50, and FIG. 8D
shows a schematic diagram of the peripheral portion 40 cut out by a
range of 50.degree. to 90.degree.. In the inclined portion 50, the
thickness is gradually decreased from the boundary (point m3, point
n2) of the first peripheral auxiliary portion 48 to the boundary of
the second peripheral portion 46 (point m4, point n3). Namely,
thickness Tmc at point m4 and thickness Tnc at point n3 have the
same height, and thickness Tmc at point m4 (thickness Tnc at point
n3) is lower than thickness Tmb at point m3 (thickness Tnb at point
n2). By smoothly connecting the first peripheral auxiliary portion
48 which is higher (thicker) than the second peripheral portion 46,
and the flat second peripheral portion 46, the inclined portion 50
functions as a buffer region. It should be noted that the inclined
portion 50 mentioned here has a surface shape, and the thickness is
always changed in the radial direction or the circumferential
direction in the plane.
[0096] The above results are summarized as follows: the region
between the predetermined rotation angle .theta.1 (50.degree.) from
the horizontal meridian 24) (0.degree.) to the rotation angle
.theta.2 (70.degree.) in the peripheral portion 40 is composed of
the first peripheral auxiliary portion 48 and the inclined portion
50, and in the case of .theta.1<.theta.<.theta.2, it is
preferable that the first peripheral auxiliary portion 48 is
arranged on one side of the inner peripheral side or the outer
peripheral side of the peripheral portion 40, and the inclined
portion 50 is arranged on the other side of the inner peripheral
side or the outer peripheral side, to thereby make both coexist and
particularly, it is preferable that the first peripheral auxiliary
portion 48 is arranged on the inner peripheral side, and the
inclined portion 50 is arranged on the outer peripheral side, to
thereby make both coexist. The region between the rotation angle
.theta.2 (70.degree.) and the vertical meridian 22 (90.degree.) is
composed of the inclined portion 50 and the second peripheral
portion 46, and in the case of .theta.2<.theta.<90.degree.,
it is preferable that the inclined portion 50 is arranged on one
side of the inner peripheral side or the outer peripheral side of
the peripheral portion 40, and the second peripheral portion 46 in
the case of having a surface shape with a uniform thickness, is
arranged on the other side of the inner peripheral side or the
outer peripheral side, and particularly, it is preferable that the
inclined portion 50 is arranged on the inner peripheral side, and
the second peripheral portion 46 is arranged on the outer
peripheral side, to thereby make both coexist. Then, it is
preferable that only the first peripheral auxiliary portion 48
(specifically, the boundary between the first peripheral portion 44
and the first peripheral auxiliary portion 48) is arranged on the
angular meridian of the rotation angle .theta.1 (50.degree.), and
only the inclined portion 50 is arranged on the angular meridian of
the rotation angle .theta.2 (70.degree.), and only the second
peripheral portion 46 is arranged on the vertical meridian 22.
[0097] In this way, exquisite axis stability is improved favorably
by providing the region where the first peripheral auxiliary
portion 48 and the inclined portion 50 coexist, and the region
where the inclined portion 50 and the second peripheral portion 46
coexist, in the detailed configuration as described above. However,
as shown in Example 2 described later, even in a case of adopting
an arrangement in which the first peripheral auxiliary portion 48
and the inclined portion 50 coexist in the area between a
predetermined rotation angle .theta. (50.degree. in the second
embodiment) to 90.degree. from the horizontal meridian 24
(0.degree.) in the peripheral portion 40, and forming the second
peripheral portion 46 as a linear portion on the vertical meridian
22, the effect of the present invention is exhibited. Namely, it is
one of the characteristics of this embodiment that the first
peripheral auxiliary portion 48 is arranged on the inner peripheral
side and the inclined portion 50 is arranged on the outer
peripheral side in a predetermined rotation angle range of the
peripheral portion 40, to thereby make both coexist.
[0098] Incidentally, rotation angle .theta.1 can be appropriately
set without being limited to the above angle and can be
appropriately set within a range of 45.degree. or more and
60.degree. or less so as to include 50.degree.. In the same way,
rotation angle .theta.2 can also be appropriately set and can be
appropriately set within a range of 55.degree. or more and less
than 90.degree. so as to include 70.degree.. However, as shown in
Examples below, .theta.1 is preferably set to 50.degree. and
.theta.2 is preferably set to 70.degree.. It should be noted that
0.degree.<.theta.1<.theta.2<90.degree. is satisfied.
[0099] Further, the first peripheral portion 44 may be set so that
the thickness becomes thinner when rotating from the horizontal
meridian 24 to the vertical meridian 22, as in the above Example
and later-described Example 1, or may be set to have uniform
thickness in a range of 0.degree. to .theta.1 when rotating from
the horizontal meridian 24 to the vertical meridian 22, and
thereafter to have thin thickness at .theta.1 to .theta.2. Further,
as in the above example, the first peripheral portion 44 may have a
surface shape, or may be linear like the second peripheral portion
46 in the above example. In this case, the following configuration
is preferable. Namely, the first peripheral portion 44 has a
boundary only with respect to the first peripheral auxiliary
portion 48, and a linear or surface-shaped second peripheral
portion 46 has a boundary only with respect to the inclined portion
50. Then, it is preferable that the first peripheral auxiliary
portion 48 and the inclined portion 50 coexist between the first
peripheral portion 44 and the second peripheral portion 46, and the
first peripheral auxiliary portion 48 is arranged on the inner
peripheral side and the inclined portion 50 is arranged on the
outer peripheral side.
[0100] Cutting planes CP0, CP100 and CP200 shown in FIG. 9A are
thick cross-sectional profiles partitioned in parallel to
horizontal meridian 24, the cutting plane CP0 is the cutting plane
on the horizontal meridian 24 (that is, 0.degree. to 180.degree.),
the cutting plane CP100 is the cutting plane including the
peripheral portion 40 near the center of the cutting plane CP100,
and the cutting plane CP200 is the cutting plane on the second
smoothing portion 42. With reference to FIG. 9B, it is found that
in the cutting plane CP0, the thickness is suddenly increased from
the edge 16, and thereafter there is no change in thickness once,
then rapidly decreased and gradually decreased toward the vertical
meridian 22. In other words, a flat surface is formed at a position
where there is no change. In this way, in the vicinity of the
horizontal meridian 24 of the peripheral portion 40, a region
having the same thickness (that is, the first peripheral portion
44) is formed. In the cutting plane CP100 (cutting plane at the
position where the horizontal meridian 24 is moved by 5.06 mm in
the vertical direction, the numerical values shown in FIGS. 9(b)
and 9(d) means a distance moved in the vertical direction), the
thickness is suddenly increased from the edge 16, and thereafter
gradually increased toward the vertical meridian 22, and there is
no change in thickness in the vicinity of the vertical meridian 22.
In the cutting plane CP200, the thickness is formed in such a
manner that although sudden increase from the edge 16 is observed,
gentle increase is observed in the vicinity of the vertical
meridian 22. In this way, it is found that in the double slab off
20, the vicinity of the both convex portions (that is, near
0.degree. and 180.degree.) of the cutting plane CP0 is much higher
(thicker) than the vicinity of the center (that is, near
90.degree.) of the cutting plane CP200.
[0101] As shown in FIG. 9C, the cutting planes CP20 to CP120 of
FIG. 9D show a sectional profile respectively, in which the
vicinity of 0.degree. to 90.degree. of the upper end portion 28 is
divided at equal intervals in parallel to the vicinity of the
cutting plane CP100. The cutting plane CP 20 is the lens
cross-section of a portion closest to the optical portion 18,
extending to the vertical meridian 22 from the edge 16 through the
second smoothing portion 42, the inclined portion 50 and the first
smoothing portion 38. Specifically, the thickness is suddenly
increased from the edge 16 to the vertical meridian 22, and
thereafter there is no change in thickness once, then, a gentle
convex shape is formed, and the thickness is decreased smoothly.
Similarly to the cutting plane CP20, the cutting plane CP 40
extends to the vertical meridian 22 from the edge 16 through the
second smoothing portion 42, the inclined portion 50 and the first
smoothing portion 38. As a whole, the thickness is gradually
changed as compared with the cutting plane CP20. Specifically, the
thickness is suddenly increased from the edge 16 to the vertical
meridian 22, and thereafter there is no change in thickness once
and a gentle convex shape is formed more smoothly than the cutting
plane CP20, and then the thickness is smoothly decreased. Cutting
plane CP60 extends to the vertical meridian 22 from the edge 16
through the second smoothing portion 42, the inclined portion 50,
the second peripheral portion 46 and the first smoothing portion
38. As a whole, the thickness is gradually changed as compared with
the cutting plane CP40. Specifically, the thickness is suddenly
increased from the edge 16 to the vertical meridian 22, and
thereafter there is no change in thickness, and a gentle convex
shape is formed more smoothly than the cutting plane CP40, and
after a smooth decrease, the change has disappeared. The cutting
plane CP80 extends to the vertical meridian 22 from the edge 16
through the second smoothing portion 42, the second peripheral
portion 46, and the first smoothing portion 38. As a whole, the
thickness is gradually changed as compared with the cutting plane
CP60. Specifically, the thickness is suddenly increased from the
edge 16 to the vertical meridian 22, and thereafter there is no
change in thickness, and a gentle convex shape is formed more
smoothly than the cutting plane CP60, and after a small decrease,
the change has disappeared. Similarly to the cutting plane CP80,
the cutting plane CP100 extends to the vertical meridian 22 from
the edge 16 through the second smoothing portion 42 and the second
peripheral portion 46. As a whole, the thickness is gradually
changed as compared with the cutting plane CP80. Specifically,
after a sudden increase from the edge 16 to the vertical meridian
22, almost no change is noticed. The cutting plane CP120 is a lens
cross section at a position closest to the lens upper end portion
28, and extends to the vertical meridian 22 from the edge 16
through the second smoothing portion 42. As a whole, the thickness
is gradually changed as compared with the cutting plane CP100.
Specifically, after a sudden increase from the edge 16 to the
vertical meridian 22, almost no change is noticed. In this way, a
flat surface (that is, the second peripheral portion 46) is formed
in the vicinity of the vertical meridian 22 of the peripheral
portion 40.
[0102] As a contact lens base material to be used for manufacturing
the contact lens 10, any copolymer may be used as long as it is a
copolymer capable of retaining the shape of the contact lens after
polymerization, or a copolymer which can be a hydrogel, or
preferably a copolymer containing silicone, which can be the
hydrogel, and (a silicone hydrogel material) which is
conventionally known as a material for soft contact lenses can be
used as it is. Further, the contact lens 10 is polymerized by a
cast molding method, and the material of the mold at this time may
be any material as long as it is a material resistant to the
monomer mixed solution, and for example, polypropylene can be
used.
[0103] Further, in the optical portion 18 of the contact lens 10,
the distance portion 32 is arranged at the center, and the first
intermediate portion 34, and the near portion 36 are arranged.
However, an optical design of the optical portion 18 for presbyopia
is not limited thereto, and it is also possible that for example
the near portion is arranged at the center, the second intermediate
portion having a power distribution continuously decreasing from
the power of the near portion, is arranged on the outer periphery
of the second intermediate portion, and the distance portion is
arranged on the outer periphery of the second intermediate
portion.
[0104] Further, the center thickness of the contact lens 10 (that
is, the center thickness in the optical portion 18) is 0.09 mm, but
the present invention is not limited thereto, and for example it is
also possible to set the center thickness in a range of 0.05 to
0.20 mm. Namely, in a case that the axis stabilizing mechanism is a
prism ballast, it is difficult to decrease the center thickness in
order to exhibit a ballast effect. However, in a case that the axis
stabilizing mechanism is the double slab off, the pinching effect
between the eyelids and eyeballs by blinking is utilized, and
therefore it is possible to set the center thickness in a range of
0.05 to 0.20 mm. The thinner the center thickness becomes, the
better the wearing feeling is achieved.
[0105] In addition, although the above embodiment is a contact
lens, the same effect can be obtained in an intraocular lens or the
like.
EXAMPLE
[0106] Hereinafter, embodiments of the present invention will be
described. For convenience of explanation, reference numerals are
omitted.
[Multifocal Toric Contact Lens]
[0107] Hereinafter, nine tests while wearing the multifocal toric
contact lens according to an example (also referred to as a bifocal
lens) will be described. Table 2(a) shows the features of Examples
1 to 3 and Comparative Examples 1 to 6, and Table 2(b) shows
parameters common to each of the multifocal toric contact lenses
used in Examples 1 to 3 and Comparative Examples 1 to 6. Regarding
the switching points and angles shown in Table 2(a), only an angle
(0.degree. to 90.degree.) near the nose-side eyebrow is indicated,
because all of the lenses under test have mirror image symmetry
vertically and horizontally, for example, corresponding to
"130.degree., 230.degree., 310.degree." in the case of "50.degree.
" and "110.degree. to 130.degree., 230.degree. to 250.degree., and
290.degree. to 310.degree. " in the case of "50.degree. to
70.degree. ". Each of the peripheral portions of Examples 1 to 3
and Comparative Examples 1 to 6 which will be described later has a
shape that is maximized on the horizontal meridian, and minimized
on the vertical meridian.
TABLE-US-00001 TABLE 2a Arrangement Thickness (mm) of peripheral
portion First Upper stage: Position of point .beta. at outside (n1
Switching First peripheral Second
(horizontal)-n2(q1)-n3(q2)-n4(vertical)) Shape of point peripheral
auxiliary Inclined peripheral Lower stage: Position of point
.alpha. at inside (m1 peripheral portion .theta.1 .theta.2 portion
portion portion portion (horizontal)-m2(q1)-m3(q2)-m4(vertical))
Example 1 Ellipse 50.degree. 70.degree. 0.degree.~50.degree.
50.degree.~70.degree. 50.degree.~90.degree. 70.degree.~90.degree.
0.3~0.2~0.15~0.15 0.3~0.2~0.2~0.15 Example 2 Ellipse 30.degree.
50.degree. 0.degree.~50.degree. 50.degree.~90.degree.
50.degree.~90.degree. 90.degree. 0.28~0.28~0.17~0.15
0.28~0.28~0.17~0.17 Example 3 Ellipse 30.degree. 50.degree.
0.degree.~50.degree. 50.degree.~90.degree. 50.degree.~90.degree.
90.degree. 0.24~0.24~0.18~0.15 0.3~0.3~0.18~0.18 Com. Ex. 1 Perfect
30.degree. -- 0.degree.~30.degree. -- -- 30.degree.~90.degree.
0.28~0.15~0.15 circle Com. Ex. 2 Perfect 30.degree. --
0.degree.~90.degree. -- -- 90.degree. 0.28~0.2~0.125 circle Com.
Ex. 3 Perfect 50.degree. 70.degree. 0.degree.~90.degree. -- --
90.degree. 0.2~0.18~0.12~0.12 circle 0.25~0.22~0.17~0.15 Com. Ex. 4
Ellipse 30.degree. -- 0.degree.~30.degree. -- -- 90.degree.
0.28~0.28~0.1 Com. Ex. 5 Ellipse 50.degree. -- 0.degree.~50.degree.
-- -- 50.degree.~90.degree. 0.28~0.15~0.15 Com. Ex. 6 Ellipse
20.degree. 60.degree. 0.degree.~90.degree. -- -- 90.degree.
0.35~0.35~0.2~0.2 0.35~0.35~0.25~0.25 Com. Ex. = Comparative
Example
TABLE-US-00002 TABLE 2b Base curve (BC) 8.6 Optical center
thickness (CT) 0.09 mm Total diameter (Dia) 14.2 mm Myopic power
(S-power) -3.00 D Astigmatic power (C-power) -0.75 D Axis (Ax)
180.degree. Addition power (Add) +1.5 D
[0108] Similarly to the contact lens 10 of the embodiment, the
multifocal toric contact lenses of Examples 1 to 3 respectively has
a first peripheral portion, a second peripheral portion, a first
peripheral auxiliary portion and an inclined portion in an
elliptical peripheral portion. For example, the second peripheral
portion in Example 1 has a constant thickness surface at point
m4-point n4-point n3, and the inclined portion has a surface at
point m4-point n3-point n2-point m3, and the first peripheral
auxiliary portion has a surface of a constant thickness at point
m3-point m2-point n2, and the first peripheral portion has a
surface at point m2-point n2-point n1-point m1. Further, in example
1, the first peripheral portion is set so that the thickness
becomes thinner as it rotates from the horizontal meridian to the
vertical meridian (that is, as it progresses in a circumferential
direction from 0.degree. to 90.degree.). Further, the second
peripheral portion in Example 2 is a linear portion at point m4 to
point n4, the inclined portion has a surface at point m4-point
n4-point n3, the first peripheral auxiliary portion has a surface
of constant thickness at point m4-point m3-point n3, and the first
peripheral portion has a surface at point m3-point n3-point
n1-point m1. Further, in example 2, when rotating from the
horizontal meridian to the vertical meridian, the thickness is set
to be uniform from 0.degree. to .theta.1, and thereafter becomes
thinner from .theta.1 to .theta.2. Further in example 3, although
having almost the same configuration as in Example 2, difference is
that the thickness is not constant when viewed in the radial
direction in the first peripheral portion (the thickness is not
uniform between the inner peripheral side and the outer peripheral
side).
[0109] In contrast, Comparative Example 1 shows a multi-focal toric
contact lens having a conventional double slab off, and a maximum
thickness portion is located on the horizontal meridian, the
thickness on the vertical meridian becomes thin, and the peripheral
portion has a perfect circle (concentric circle). However, in
Comparative Example 1, unlike the above embodiment, the thickness
is controlled on one circumferential line. Namely, in Comparative
Example 1, the portion on one circumferential "line" under
thickness control is the peripheral portion. In contrast, the
peripheral portion in the present invention includes a first
peripheral auxiliary portion having a "surface shape" and an
inclined portion having a "surface shape". Therefore, the portion
on the circumferential line in Comparative Example 1 obviously does
not have the first peripheral auxiliary portion having the surface
shape and the inclined portion having the surface shape, and is
totally different from the peripheral portion of the present
invention. Accordingly, in Table 4 (area ratio of each portion),
Comparative Example 1 shows that the peripheral portion is a
portion on the circumferential line and there is no area. Therefore
there is no value of the area ratio in the column of the peripheral
portion. Instead, the area ratio is described in a form of
combining the first smoothing portion or the second smoothing
portion with the peripheral portion, in consideration of the
peripheral portion as a circumferential line. Further, even in a
case of the portion on the circumferential line, there are cases
that the minimum thickness portion and the maximum thickness
portion may exist, and therefore it is assumed that the second
peripheral portion and the first peripheral portion also exist in
the first comparative example and based on this assumption,
explanation will be given hereafter.
[0110] Further, Comparative Example 2 shows a multi-focal toric
contact lens whose thickness is gradually thinned from 0.degree. to
90.degree. based on Comparative Example 1. However, as in
Comparative Example 1, neither the first peripheral auxiliary
portion nor the inclined portion nor the constant thickness surface
exists, and there is no surface with constant thickness.
Comparative Example 3 shows a multifocal toric contact lens having
a shape in which two switching points of thickness are provided
based on Comparative Example 1. However, even if the portion on the
vertical meridian is defined as the second peripheral portion, the
outside has a constant thickness in the circumferential direction
in the portion adjacent to the second peripheral portion (.theta.2
to 90.degree.). Therefore, the inclined portion does not exist in
Comparative Example 3. Further, there is no first peripheral
auxiliary portion having a surface shape in which the thicknesses
are equal in the plane. Therefore, the first peripheral auxiliary
portion does not have the inclined portion in Comparative Example
3. In Comparative Examples 1 and 2, one kind of thickness is
annularly specified at plural angles, and in Comparative Example 3,
plural kinds of thicknesses are annularly specified at plural
angles.
[0111] Further, Comparative Example 4 shows a multi-focal toric
contact lens in which based on Comparative Example 1, the portion
from the horizontal meridian to 30.degree. is taken as the maximum
thickness portion, and an elliptical peripheral portion is formed
by bringing the thickness specified on the vertical meridian closer
to the optical portion side. Similarly to Comparative Example 1,
neither the first peripheral auxiliary portion nor the inclined
portion exists. Comparative Example 5 shows a multi-focal toric
contact lens in which based on Comparative Example 1, the switching
point is changed from 30.degree. to 50.degree., a maximum thickness
portion is set on the horizontal meridian, and an elliptical
peripheral portion is formed by bringing the thickness specified on
the horizontal meridian closer to the optical portion side.
Similarly to Comparative Example 1, neither the first peripheral
auxiliary portion nor the inclined portion exists. The long axis of
the peripheral portion in Comparative Examples 3 and 4 is on the
horizontal meridian, and the long axis of the peripheral portion in
Comparative Example 5 is on the vertical meridian.
[0112] Moreover, the multifocal toric contact lens of Comparative
Example 6 has an elliptical peripheral portion, in which the
maximum thickness portion is located on the horizontal meridian,
and has a largest thickness part at a portion from the horizontal
meridian to 20.degree.. Similarly to Comparative Example 3, even if
the portion on the vertical meridian is defined as the second
peripheral portion, the thickness is constant in the
circumferential direction both inside and outside in the portion
adjacent to the second peripheral portion (.theta.2 to 90.degree.).
Therefore, the inclined portion does not exist in Comparative
Example 6. Therefore, it is impossible to specify the first
peripheral auxiliary portion adjacent to the inclined portion, and
as a result, neither the first peripheral auxiliary portion nor the
inclined portion exists in Comparative Example 6. In Comparative
Examples 4 and 5, one kind of thickness is specified as elliptical
shapes at plural angles, and in Comparative Example 6, plural kinds
of thicknesses are specified as elliptical shapes at plural
angles.
[0113] Wearing tests were carried out on one side of eyes of five
testees of different ages. The axial position after 15 minutes
wearing was confirmed and the results are shown in Table 3(a).
Table 3(b) shows an explanation for the symbols shown in Table
3(a). As a criterion of evaluation, satisfying the case of the
following two conditions is applied: "Average point is 6.0 points
or higher" and ".times.evaluation: that is, there is no testee
whose evaluation score is 0", and other cases were regarded as
being inapplicable.
TABLE-US-00003 TABLE 3a A B C D E Average point Judgement Example 1
.largecircle. .largecircle. .largecircle. .largecircle.
.tangle-solidup. 8.8 Applicable Example 2 .largecircle.
.largecircle. .tangle-solidup. .tangle-solidup. .DELTA. 7
Applicable Example 3 .tangle-solidup. .largecircle. .DELTA.
.tangle-solidup. .DELTA. 6.4 Applicable Com. Ex. 1 X
.tangle-solidup. .tangle-solidup. X .DELTA. 3 inapplicable Com. Ex.
2 X .largecircle. .largecircle. X .largecircle. 6 inapplicable Com.
Ex. 3 .tangle-solidup. X .largecircle. X .largecircle. 4.8
inapplicable Com. Ex. 4 X .tangle-solidup. .largecircle.
.tangle-solidup. .largecircle. 5.6 inapplicable Com. Ex. 5 X X
.DELTA. .DELTA. X 2.8 inapplicable Com. Ex. 6 .tangle-solidup.
.largecircle. .largecircle. .DELTA. X 6.2 inapplicable Com. Ex. =
Comparative Example
TABLE-US-00004 TABLE 3b Definition of axis misalignment Symbol
Evaluation point Misalignment .largecircle. 10 0.degree. or more,
less than 15.degree. .DELTA. 7 15.degree. or more, less than
25.degree. .tangle-solidup. 4 25.degree. or more, less than
35.degree. X 0 35.degree. or more, 45.degree. or less
[0114] As shown in Table 3(a), the axis stability was better in
Examples 1 to 3 than in Comparative Examples 1 to 6.
[0115] Table 4 shows the ratio of a surface area of a front surface
with respect to each part of the double slab off. Here, it was
revealed that the axis stability was remarkably improved when the
peripheral portion was about (preferably less than) 10% or less of
the front surface. The double slab off in Comparative Examples 1,
2, 4, and 5, is divided into the first smoothing portion and the
peripheral portion, and the peripheral portion and the second
smoothing portion, because the peripheral portion sandwiched
between the first smoothing portion and the second smoothing
portion is a boundary having no width (that is, points .alpha. and
.beta. are located at the same position). In contrast, the double
slab off in Examples 1 to 3, Comparative Example 3, and Comparative
Example 6, is divided into the first smoothing portion, the
peripheral portion, and the second smoothing portion, because the
peripheral portion sandwiched between the first smoothing portion
and the second smoothing portion has a width (that is, point
.alpha. and point .beta. have a predetermined distance at any
angle).
TABLE-US-00005 TABLE 4 First First smoothing Peripheral portion +
Second smoothing portion + peripheral Peripheral second smoothing
smoothing portion portion portion portion portion Example 1 14 -- 9
-- 34 Example 2 5 -- 8 -- 45 Example 3 10 -- 13 -- 35 Com. Ex. 1 --
25 -- 34 -- Com. Ex. 2 -- 15 -- 42 -- Com. Ex. 3 1.5 -- 15 -- 25
Com. Ex. 4 -- 11 -- 47 -- Com. Ex. 5 -- 20 -- 38 -- Com. Ex. 6 12
-- 15 -- 30 Com. Ex. = Comparative Example
[0116] The above results are summarized as follows: the multifocal
toric contact lenses of Examples 1 to 3 have improved axis
stability, compared to those of Comparative Examples 1 to 6 having
no first peripheral portion, second peripheral portion, first
peripheral auxiliary portion, and inclined portion, in the
elliptical peripheral portion. Further, it was revealed that the
axis stability was remarkably improved when the peripheral portion
was about (preferably less than) 10% or less of the front
surface.
[Toric Contact Lens]
[0117] In another embodiment, six tests while wearing a toric
contact lens (also referred to as an astigmatic lens) of the
present invention will be described. Table 5(a) shows the features
of Examples 4 and 5 and Comparative Examples 7 to 10, and Table5(b)
shows parameters common to each of the toric contact lenses used in
Examples 4 and 5 and Comparative Examples 7 to 10. Each of the
peripheral portions of Examples 4 and 5 and Comparative Examples 7
to 10 which will be described later has a shape having a maximum
thickness on the horizontal meridian, and has a shape having a
minimum thickness on the vertical meridian.
TABLE-US-00006 TABLE 5a Arrangement Thickness of the peripheral
portion (nm) First Upper stage: Position of point .beta. at outside
(n1(horizontal)- Shape of the Switching First peripheral Second
n2(.theta.1)-n3(.theta.2)-n4(vertical)) peripheral point peripheral
auxiliary Inclined peripheral Lower stage: Position of point
.alpha. at inside (m1(horizontal)-m2 portion .theta.1 .theta.2
portion portion portion portion
(.theta.1)-m3(.theta.2)-m4(vertical)) Example 4 Ellipse 50.degree.
70.degree. 0.degree.~50.degree. 50.degree.~70.degree.
50.degree.~90.degree. 70.degree.~90.degree. 0.3~0.2~0.15~0.15
0.3~0.2~0.2~0.15 Example 5 Perfect 50.degree. 70.degree.
0.degree.~50.degree. 50.degree.~70.degree. 50.degree.~90.degree.
70.degree.~90.degree. 0.3~0.2~0.15~0.15 circle 0.3~0.2~0.2~0.15
Com. Ex. 7 Perfect -- -- 0.degree.~90.degree. -- -- 90.degree.
0.3~0.15 circle Com. Ex. 8 Ellipse 50.degree. 70.degree.
0.degree.~70.degree. -- -- 70.degree.~90.degree. 0.3~0.2~0.15~0.15
Com. Ex. 9 Perfect 50.degree. -- 0.degree.~50.degree. -- --
50.degree.~90.degree. 0.3~0.2~0.15 circle Com. Ex. 10 Perfect
50.degree. 70.degree. 0.degree.~90.degree. -- --
70.degree.~90.degree. 0.25~0.2~0.15~0.15 circle 0.3~0.23~0.18~0.15
Com. Ex. = Comparative Example
TABLE-US-00007 TABLE 5b Base curve (BC) 8.6 Optical center
thickness (CT) 0.08 mm Total diameter (Dia) 14.2 mm Myopic power
(S-power) -3.00 D Astigmatic power (C-power) -0.75 D Axis (Ax)
180.degree.
[0118] In the toric contact lens of Example 4, the optical portion
of Example 1 is simply changed from a design for presbyopia and
astigmatism to a design for astigmatism, and the same double slab
off as in Example 1 is included. Example 5 shows a toric contact
lens with a peripheral portion as a perfect circle based on Example
4.
[0119] In contrast, Comparative Example 7 shows a toric contact
lens with a conventional double slab off, in which the peripheral
portion is a perfect circle, and as in Comparative Example 1,
neither the first peripheral auxiliary portion nor the inclined
portion is included. Comparative Example 8 shows a toric contact
lens in which the peripheral portion based on Comparative Example 6
is an ellipse, and as in Comparative Example 1, neither the first
peripheral auxiliary portion nor the inclined portion are included.
Comparative Example 9 shows a toric contact lens based on Example
4, in which the peripheral portion is a perfect circle, and as in
Comparative Example 1, neither the first peripheral auxiliary
portion nor the inclined portion is included. Comparative Example
10 shows a toric contact lens based on Example 4, in which the
peripheral portion is a perfect circle, and although the second
peripheral portion is included, a range from 0.degree. to
90.degree. is the first peripheral portion (0.degree. to 90.degree.
inside, 0.degree. to 70.degree. outside), and neither the first
peripheral auxiliary portion nor the inclined portion is included.
In Comparative Examples 7 and 9, one kind of thickness is annularly
specified at plural angles, and in Comparative Example 8, plural
kinds of thicknesses are specified as elliptical shapes at plural
angles, and in Comparative Example 10, plural kinds of thicknesses
are annularly specified at plural angles.
[0120] Wearing tests of Examples 4 and 5 and Comparative Examples 7
to 10 were also carried out in the same manner as in the wearing
test shown in Table 3(a). Results of the axis position are shown in
Table 6. Note that symbols shown in Table 6 are the same as those
in Table 3(b).
TABLE-US-00008 TABLE 6 A B C D E Average point Judgement Example 4
.DELTA. .largecircle. .largecircle. .tangle-solidup. .DELTA. 7.6
Applicable Example 5 .DELTA. .largecircle. .DELTA. .largecircle.
.largecircle. 8.8 Applicable Com. Ex. 7 .DELTA. .tangle-solidup.
.tangle-solidup. .tangle-solidup. .DELTA. 5.2 Inapplicable Com. Ex.
8 .tangle-solidup. .DELTA. .tangle-solidup. .DELTA. .DELTA. 5.8
Inapplicable Com. Ex. 9 .tangle-solidup. .largecircle.
.tangle-solidup. .largecircle. X 5.6 Inapplicable Com. Ex. 10 -- X
.largecircle. X .tangle-solidup. 3.5 Inapplicable Com. Ex. =
Comparative Example
[0121] The above results are summarized as follows: the toric
contact lens of examples 4 and 5 have improved axis stability,
compared to those of Comparative Examples 7 to 10 having neither a
part of nor all of the elliptical peripheral portion, the first
peripheral portion, the second peripheral portion, the first
peripheral auxiliary portion, nor the inclined portion. In Example
5, the shape of the peripheral portion is not an elliptical shape
but a perfect circle and an annular shape, but the toric contact
lens of Example 5 is sufficiently effective as described above.
Therefore, the shape of the peripheral portion in the present
invention is not limited to the elliptical shape and the annular
shape.
[Contact Lens for Myopia/Hyperopia]
[0122] In yet another embodiment, two tests while wearing the
contact lenses for myopia and hyperopia of the present invention
will be described. Table 7(a) shows the features of Example 6 and
Comparative Example 11, Table 7(b) shows the parameters common to
each of the contact lenses used in Example 6 and Comparative
Example 11.
TABLE-US-00009 TABLE 7a Arrangement Thickness of the peripheral
portion (nm) First Upper stage: Position of point at outside (n1
Shape of Switching First peripheral Second
(horizontal)-n2(.theta.1)-n3(.theta.2)-n4(vertical)) the peripheral
point peripheral auxiliary Inclined peripheral Lower stage:
Position of point .alpha. at inside (m1 portion .theta.1 .theta.2
portion portion portion portion
(horizontal)-m2(.theta.1)-m3(.theta.2)-m4(vertical)) Example 6
Ellipse 50.degree. 70.degree. 0.degree.~50.degree.
50.degree.~70.degree. 50.degree.~90.degree. 70.degree.~90.degree.
0.3~0.2~0.15~0.15 0.3~0.2~0.2~0.15 Com. Ex. 11 Perfect -- --
0.degree.~90.degree. -- -- 90.degree. 0.3~0.15 circle Com. Ex. =
Comparative Example
TABLE-US-00010 TABLE 7b Base curve (BC) 8.6 Optical center
thickness (CT) 0.07 mm Total diameter (Dia) 14.2 mm Myopic power
(S-power) -3.00 D
[0123] In the contact lens of Example 6, the optical portion of
Example 1 is simply changed from a design for presbyopia and
astigmatism to a design for myopia/hyperopia, and the double slab
off of Example 1 is included.
[0124] In contrast, the contact lens of Comparative Example 11 is a
contact lens for myopia and hyperopia having the conventional
double slab off, in which the peripheral portion is a perfect
circle, and as in Comparative Example 7, neither the first
peripheral auxiliary portion nor the inclined portion is included.
Note that in Comparative Example 11, one kind of thickness is
elliptically specified at plural angles, and in Example 6, plural
kinds of thicknesses are annularly specified at plural angles.
[0125] The wearing tests described in Example 6 and Comparative
Example 11 were carried out in the same manner as the wearing test
shown in Table 3(a), and results of the axis position are shown in
Table 8. Note that symbols shown in Table 8 are the same as those
in Table 3(b).
TABLE-US-00011 TABLE 8 A B C D E Average point Judgement Example 6
.tangle-solidup. .largecircle. .largecircle. .largecircle. .DELTA.
8.2 Applicable Com. Ex. 11 .tangle-solidup. .DELTA.
.tangle-solidup. .tangle-solidup. .largecircle. 5.8 Inapplicable
Com. Ex. = Comparative Example
[0126] Table 8 reveals that the contact lens of Example 6 having
all features of the present invention has improved axis stability,
compared to a conventional spherical lens of Comparative Example
11.
[0127] The above results are summarized as follows: the contact
lens of Example 6 for myopia has improved axis stability, compared
to that of Comparative Example 11 having neither the first
peripheral portion, the second peripheral potion, the first
peripheral auxiliary portion, nor the inclined portion in the
elliptical peripheral portion.
[0128] Note that even in the contact lenses for myopia and
hyperopia, the content described in the problem of the present
invention, that is, the problem of stabilizing the posture of the
lens may occur. For example, when wearing lenses among color
contact lenses containing designs or patterns, or when the pattern
has a vertical direction, it is necessary to wear the lens while
correcting the vertical direction. In this case, it is impossible
to correctly show the patterns unless the posture of the lens is
stabilized like the toric contact lens. Therefore, even in the
above-described contact lens for myopia, there arises a problem of
stabilizing the posture of the lens, and as a means for solving
this problem, the above-described examples and the configuration
described in the above-described embodiment are employed, and it is
possible to exhibit the effect of stabilizing the posture of the
lens.
DESCRIPTION OF SIGNS AND NUMERALS
[0129] 10 Multifocal contact lens [0130] 12 Front surface (front
curve) [0131] 14 Rear surface (base curve) [0132] 16 Edge [0133] 18
Optical portion [0134] 20 Double slab off [0135] 22 Vertical
meridian [0136] 24 Horizontal meridian [0137] 26 Angular meridian
[0138] 28 Lens upper end portion [0139] 30 Lens lower end portion
[0140] 32 Distance vision portion [0141] 34 First intermediate
portion [0142] 36 Near vision portion [0143] 38 First smoothing
portion [0144] 40 Peripheral portion [0145] 42 Second smoothing
portion [0146] 44 First peripheral portion [0147] 46 Second
peripheral portion [0148] 48 First peripheral auxiliary portion
[0149] 50 Inclined portion [0150] L Two dot chain line
* * * * *